VIRGIN RIVER HOME

NEWS

INSECT MONITORING

VEGETATION RESPONSES AND RESTORATION

HYDROLOGICAL RESPONSES

AVIAN RESPONSES

REPTILE/AMPHIBIAN RESPONSES

MAMMAL RESPONSES

COLLABORATORS AND LINKS

LITERAURE

Insect Monitoring

Diorhabda beetles on tamarisk branch Photo by Tom Dudley

Dr Dudley Inspecting Tamarisk branches

Completed in 2009
            Biocontrol agent progress  Bi-weekly monitoring of Diorhabda population size and developmental condition in and upstream of Virgin Valley, and monthly mapping of their dispersal in the Virgin watershed, were conducted through the period of beetle activity. Adult beetles were collected to determine developmental condition (date of entry into reproductive/ winter diapause) to determine potential asynchrony with environmental conditions (daylength) at this low latitude. Live beetles are also retrieved to the lab where we can monitor genetic changes that have occurred to determine how rapidly they are adapting to this latitude and how far south they can survive, in particular whether they have the capacity to establish further south including the lower Colorado River. Overwinter survival studies are also underway.
            Invertebrate community  Pit fall traps and sweep net sampling were used to assess invertebrate community composition at 12  sites along the Arizona and Nevada segments of the Virgin River during the summer of 2009. Assessments were made in Tamarisk-dominant and Tamarisk/native mixed habitats and will be compared with data collected after beetles have become established to determine invertebrate community responses to beetles, particularly potential enhancement of native insect predators feeding on this new prey resource.

2010 Objectives
            Biocontrol agent progress  Monitoring of the Diorhabda population will continue in 2010 in this watershed and beyond to document continued spread, the length of their active period and related genetic changes. Laboratory studies will address the potential for sustaining reproductive and overwintering populations, and capacity for natural selection to facilitate southward expansion.
            Invertebrate community  Pit-fall trap sampling will continue as well and additional invertebrate sampling will be initiated to support the avian monitoring component of the project.  This sampling will be geared toward assessing the abundance of various invertebrate food resources available to birds at nest sites where beetles are present versus absent.  By knowing the relative abundance of different invertebrate food types and monitoring the use of these types at the nest with video cameras, we can determine whether birds show a preference for beetles as a food resource (use them more frequently than their relative abundance would predict) or use them as a backup food resource (use them less frequently than their relative abundance would predict).  Similar invertebrate sampling will support reptile and small mammal studies.

 

Researchers: T. Dudley, Ryan Ganjtomari, Sherri Pucherelli, Matt Allen, Dan Bean, Levi Jamison